A fuel supply system having a low pressure region, a pumping device to deliver fuel from the low pressure region to a high pressure region. In the high pressure region between the pumping device and injectors there is a pressure storage system that is permanently under high pressure. The pressure storage system has a plurality of distributor units each with at least three connections connected in series. A respective injector connection of each distributor unit is connected to at least one injector each via a high pressure line that is under high pressure at times dependent on the injection cycle. Each distributor unit of the pressure storage system is assigned an individual leakage detection device. Each distributor unit is assigned a non-return valve, which allows a leakage flow starting out from the respective distributor unit in the direction of the pumping device.

A connector block that directs fuel from an outer fuel line to an inner fuel line. The connector block includes an inlet that couples to the outer fuel line, an outlet that coupled to the inner fuel line, and a fuel accumulator fluidly coupled to the inlet and the outlet. The fuel accumulator directs the fuel from the inlet to the outlet.

Methods and systems are providing for improving zero flow lubrication (ZFL) of a high pressure fuel pump coupled to direct fuel injectors via a direct injection fuel rail. A ZFL transfer function for the fuel pump is learned while fuel is at non-nominal fuel bulk modulus conditions and corrected for variations from a nominal fuel bulk modulus estimate. When zero flow lubrication of the pump is requested, the pump is operated with a duty cycle based on the learned transfer function and an instantaneous estimate of the fuel bulk modulus to compensate for differences in fuel condition from the nominal fuel bulk modulus estimate.

A fuel system includes a low-pressure fuel delivery unit; a high-pressure fuel delivery unit which has a drive region and a delivery region such that the drive region supplies fuel to the delivery region and such that the delivery region supplies fuel to a high-pressure fuel injector; a low-pressure fuel supply passage which supplies fuel from the low-pressure fuel delivery unit to the drive region of the high-pressure fuel delivery unit; a cooling passage which receives fuel from the drive region of the high-pressure fuel delivery unit; and a low-pressure fuel injector supply passage which is in direct fluid communication with the low-pressure fuel supply passage and which supplies fuel to a low-pressure fuel injector from the cooling passage.

Methods and systems are provided for a direct injection fuel pump. In one example, pressure in a step chamber of the direct injection fuel pump may be regulated to a substantially constant pressure during an entire pump cycle including a compression stroke and a suction stroke.

Methods and systems are providing for improving zero flow lubrication (ZFL) of a high pressure fuel pump coupled to direct fuel injectors via a direct injection fuel rail. A ZFL transfer function for the fuel pump is learned while fuel is at non-nominal fuel bulk modulus conditions and corrected for variations from a nominal fuel bulk modulus estimate. When zero flow lubrication of the pump is requested, the pump is operated with a duty cycle based on the learned transfer function and an instantaneous estimate of the fuel bulk modulus to compensate for differences in fuel condition from the nominal fuel bulk modulus estimate.

Methods and systems are provided for operating a high pressure injection pump to provide each of high fixed fuel pressure at a first direct injection fuel rail and high variable fuel pressure at a second direct injection fuel rail. The direct injection fuel rail pressure can be raised above a pressure provided with a lift pump via a fuel system configuration that includes various check valves, pressure relief valves, and a spill valve positioned between an inlet of the high pressure injection pump and the port injection fuel rail. Fixed and variable high pressure direct injection may be advantageously used to provide learn the ballistic region of each direct injector.

A fuel delivery system for a direct injection internal combustion engine having two fuel rails and a plurality of fuel injectors attached to and fluidly connected with each fuel rail. A first fuel pump has its output connected with the first fuel rail while a second fuel pump has its output connected with the second fuel rail. A crossover pipe fluidly connects the outlets of both the first and second pumps. Both the first pump and the second pump each have an intake stroke and a pumping stroke. Furthermore, the intake stroke of the first pump coincides with the pumping stroke of the second pump and vice versa.

Various methods are provided for characterizing fuel injector operation. In one embodiment, a method of characterizing fuel injector operation comprises determining a flow error of a single fuel injector of two or more fuel injectors positioned in a first fuel rail by comparing a sum of each of a plurality of injector commands for the single injector to a fuel amount pumped into the first fuel rail, the fuel amount being predetermined.

A first fuel rail of an engine connects to first fuel injectors and a second fuel rail connects to second fuel injectors. The first fuel injectors each includes a tip portion projecting through an opening in the cylinder head into the combustion chamber. The second fuel injectors each includes a tip portion projecting through an opening in a bottom portion of an intake port. The first fuel rail includes first mounting brackets each including an aperture, and outwardly projecting mounting bosses, and fixedly attaches to the cylinder head via fasteners that pass through the apertures of the first mounting brackets and attach to the mounting bosses of the cylinder head. The second fuel rail includes second mounting brackets each including an aperture. The second fuel rail fixedly attaches to the first fuel rail via fasteners that attach to the mounting bosses of the first fuel rail.